In plasma processing apparatus used to process substrates to be processed, such as semiconductor wafers, in the manufacturing processes of various semiconductor devices, it is important to reduce metallic contaminants which adversely affect semiconductor devices. In particular, alkali metals such as Na derived from human bodies is a contaminant giving great influence on the characteristics of the device, since it easily causes contamination via chamber internal components and has a property of moving diffusively in a semiconductor device once it is introduced in the device.
The countermeasure against Na contamination derived from human bodies, which may occur during setting-up of a plasma processing apparatus or maintenance of the plasma processing apparatus, is carried out by, opening the chamber to the atmosphere, performing a wet-cleaning of chamber internal components by using a cleaning liquid such as water of isopropyl alcohol, and further wiping the inner wall of the chamber with a wiper impregnated with water or a solvent. Further, after the cleaning, plasma conditioning is carried out over a long period of time.
However, such cleaning process including the wet cleaning and the plasma conditioning spend several hours, including the time for opening of the process chamber to the atmosphere, the time for wet cleaning, the time for re-evacuation and the time for conditioning of the process chamber. This results in a lower efficiency of semiconductor device manufacturing. Although methods of cleaning the inside of a chamber using plasma has been proposed (for example, Patent Document 1), a method effective for Na contamination has not been proposed.
Patent Document 1: Japanese Patent Laid-Open No. 1994-97075.